I've pushed driver fixes for this to master in patch:
d655a3ff423e69c19a5dc07140cbf3caaa32cb86 Remove NoAccel support.
There's an associated fix necessary in the kernel to bump the framebuffer limit from 2048 to 4096 for KMS which should land shortly.

(In reply to comment #7)
> I've pushed driver fixes for this to master in patch:
>
> d655a3ff423e69c19a5dc07140cbf3caaa32cb86 Remove NoAccel support.
>
> There's an associated fix necessary in the kernel to bump the framebuffer limit
> from 2048 to 4096 for KMS which should land shortly.
Keith, I see the xf86-video-intel fix, but I can't find the kernel fix in drm-intel-next.
X still fails to start (with 4096 set) with message: "failed to add fb"

In comment #7, it sounds like there is a fix needed for this to work with KMS enabled. With all components of the 2009Q3 release (but kernel 2.6.32-rc7) this still seems to be missing - with KMS enabled, xrandr tells me the screensize is limited to 2048x2048 still, but with KMS disabled, that goes up to 4096x4096.
Did that fix get left behind somewhere?
I ask partly because it appears framebuffer compression gets disabled (according to Xorg.0.log anyway) if KMS is not enabled, so it would appear that at the moment one has to choose between bigger screens (no KMS) or framebuffer compression (KMS).

Sorry, I'm a moron. Thanks for the quick answers.
I got that backwards. It appears to me as though large screens only work if KMS is enabled, and framebuffer compression gets disabled if KMS is enabled.
(on a 945GME - in a dell mini-9).

(In reply to comment #19)
> Sorry, I'm a moron. Thanks for the quick answers.
>
> I got that backwards. It appears to me as though large screens only work if
> KMS is enabled,
That's expected.
> and framebuffer compression gets disabled if KMS is enabled.
That's probably bug#23767. I'm going to reopen it.